Superheterodyne radio-receiving set



June 24, 1952 VAN W SUPERHETERODYNE RADIO RECEIVING SET Filed March 26,1948 RECZYHER 02's. Mime OJCILLAJUR T0 ALARM H 1 m N VM E m M T H W B Lm A Patented June 24, 1952 U N I T E D S TAT E S PATENT Fr'I C-ESUPERHETERODYNE RADIO-RECEIVING SET Adelbert van Weel, Eindhoven,Netherlands, as-

signor to Hartford National Bank and Trust Company, Hartford, Conn., astrustee Application March 26, 1948, Serial No. 17,158 In the NetherlandsApril 8, 1947 upon the disappearance of the intermediate-Hequency-voltage. It applies particularly to radio communication systemsin which transmission is effected by means of a transmitter and areceiver. In such systems it is of importance that upon failure of thereceiver an arrangement becomes operative by which the disturbance isindicated by means of an alarm system or change over is effected to aspare receiver, so that interruption of the communication is reduced asmuch as possible.

It is known to utilise in such apparatus the presence or absence of anintermediate-frequency output voltage as an indication of perfectoperation of the receiver. The conventional circuit arrangements have,however, the disadvantage that even on the occurrence of a disturbancein the transmitter, i. e. when an alarm or change over at the receiverend is not at all necessary, the intermediate-frequency output voltagemay drop out due to which the alarm system or the change overarrangement would become operative.

To avoid this disadvantage, according to the invention, an additionaloscillator is provided which produces a voltage, of which the frequencycorresponds to the incoming frequency and which is fed to the inputcircuit of the receiving set, the said oscillator being controlled bythe intermediate-frequency voltage in such manner that it is operativeonly in the absence of the intermediate- ,frequency voltage or if thislies below a given small value.

' The value of the voltage of the additional oscillator operative in theinput circuit should be smaller than the normal intensity of theincoming signal, since otherwise instability may occur.

In order that the invention may be clearly understood and readilycarried into effect it will now be described more fully with referenceto the accompanying drawing, given by way of example. The sole figurerepresents diagrammatically in block form the circuit arrangement of thesuperheterodyne receiver, in which the invention is used.

which the loudspeaker 6 or another reproducing device is connected.

According to the invention, in order to trace whether, upondisappearance of the intermediate-frequency output voltage, thedisturbance has occurred in the receiver or in the transmitter inquestion, an additional oscillator l is incorporated in the receiver,which oscillator produces a voltage, of which the frequency correspondsto the frequency of the incoming oscillations, a

part of this voltage being supplied, through the lead 8, to the inputterminals of the receiver. This voltage is smaller than that which isnormally supplied by the transmitter, through the antenna I, to theinput of the receiver. Part of the intermediate-frequency output energyis rectified by the rectifier 9 and used for controlling the additionaloscillator 1. This is efiected in such manner that in the presence ofthe normal antenna signal the oscillator I does not oscillate.

If the antenna signal fails due to a disturbance in the transmitter, theoscillator I becomes operative so that notwithstanding that anintermediate-frequency output voltage subsists an alarm or change overto the spare receiver does not occur.

If, however, a disturbance occurs in the receiver, theintermediate-frequency output signal drops out at any rate, so thatchanging over to the spare receiver takes place or an alarm signal isproduced.

What I claim is:

l. A superheterodyne receiver for actuating an element for indicatingcontinuity of the transmission path of the receiver, comprising inputmeans for an input signal wave, means to convert the signal wave into anintermediate frequency signal wave, an oscillator for producing agenerated wave having a frequency substantially equal to said inputsignal wave, means to couple the oscillator to said input means therebyto apply said generated wave to said input means, means coupled to saidtransmission path and responsive to an intermediate frequency signalwave having an amplitude greater than a given value to de-energize saidoscillator, and means coupled to said transmission path to actuate saidindicating element in the absence of an intermediate frequency wave.

2. A superheterodyne receiver for actuating an element for indicatingcontinuity of the transmission path of the receiver, comprising inputmeans for an input signal Wave, means to convert the signal wave into anintermediate frequency signal wave, an intermediate frequency 3amplifier coupled to said conversion means, an oscillator for producinga generated Wave having a frequency substantially equal to said inputsignal wave, means to couple the oscillator to the 4 ing an amplitudegreater than a given value to de-energize said oscillator, and meanscoupled to said transmission path for actuating said indicating elementin the absence of a wave in said input means thereby to apply saidgenerated 5 intermediate frequency amplifier.

Wave to said input means at an amplitude level lower than the level ofthe input signal wave, de tector means coupled to the intermediatefrequency amplifier and to the oscillator and responsive to anintermediate frequency wave hav- 10 ADELBERT VAN WEEL.

No references cited.

